New Gauges Now Alternator Not Charging

[95strokerPSU]

I got rid of the stock cluster and all my new gauges are wired in and everything is fine except my alt isn't charging. The only thing I can think of is the wire that goes to charge indicator light needs to be grounded. Here's a diagram, it's the light green/red wire... http://www.veryuseful.com/mustang/tech/engine/images/Mustang-94-95-Alt.gif

What do you guys think?

 

[AznStanger3v]

when you say it isnt charging, di you put a dmm to the back of the alternator?

or

are you saying the guage isnt displaying a charge?

if the alternator is barely charging at the battery, then id look at the CI wire. it doesnt need to be grounded from the looks of the schematic.

 

[HISSIN50]

Dave, you are on the right track. Some theory:

You're dealing with the Ignition terminal for your regulator. With the key on, 12 volts goes through this wire and the battery warning light. The regulator grounds the other end of this wire when the alternator is not excited (which makes your battery light illuminate). Once the alternator excites, it removes the ground from this circuit, which allows the battery light to go out.

If the alt does not see this ignition wire go hot, the alt will not excite. As you noted, that's likely your issue.

The resistor you see in parallel with the battery bulb is a safeguard for the ignition circuit (so a burned out bulb doesnt leave you stranded with no alternator charging).

Once you connect this wiring back up Dave, you should be ok. One thing: ensure that you keep bulbs and the resistor in the wiring. Otherwise, you can see that you would have 12 volts grounding in the regulator. Not good.

Good luck bud.

 

[95strokerPSU]

JT, first off thanks for your reply.

So I guess I'll need to get a bulb and attach the light green/red wire to one post and then the red/light green wire on the other post of the bulb. Does that sound right? Also put a resistor in line.

 

[HISSIN50]

Sounds good. The resistor should be along the lines of a 500 Ohmer, IIRC.

And be sure it's in parallel (not in-series) with the bulb you use. The legs of the resistor need to circumvent the bulb (so a bad bulb is not an impediment to electron flow to the regulator - in such an event, all the juice would go through the resistor's pathway instead).

If this is something like a Florida 5.0 Cluster, you should be good to go (I've helped a couple guys wire these up and they had the same issue).

I've been wondering what you've been up to. I've seen your part ads and you had me worried.

Good luck Dave.

 

[95strokerPSU]

Can I just use a resistor and no bulb?

 

[HISSIN50]

Can I just use a resistor and no bulb?

I've not considered it but I dont see why not. This particular circuit in the alternator wiring has been the same on Fords for about half a century, and in that time, I'd bet some car came without a battery/amp light. A bulb is just a resistor of sorts anyhow, and the resistor in the OEM wiring is for the purpose of having a bulb burn out.

(I'm very confident that this will work, but I have NOT tried it, so I outlined the logic of why I think it should work fine - hence the thinking aloud above. When I haven't done something myself, I like to show my thought process rather than just tossing out an obligatory go for it. ).